Abstract: The initial forms of tensile membrane structures can not be selected arbitrarily. They must satisfy static equilibrium and architectural need. Based on geometrical nonlinear finite element theory, a curved quadrilateral isoperimetric element with 8 nodes for initial form analysis of tensile membrane structures is presented. The components caused by the element curvatures are added to the equilibrium equations by establishing curvilinear coordinates. The expressions of the element stiffness matrix and the nodal force array are derived. Newton - Raphson iteration method is adopted to solve nonlinear equations. Numerical examples indicate that this method is efficient, reliable, and stable.